Environmental challenges such as maternal alcohol exposure, smoking, or malnutrition, likely leave their mark on the developing fetus via epigenetic changes, particularly changes in DNA methylation. Epigenetic changes can be a marker of past environmental challenges, but can also lead to disease. The placenta, an easily available tissue for study, is ideal for identifying significant epigenetic changes associated with early fetal alcool exposure. Here we utilize a unique data set, placentas collected by the Safe Passage Study (PASS), to conduct the first study to measure the potential effect of alcohol exposure in placenta methylation. We will measure genome wide methylation using the Illumina 450k methylation array technology in a paired sample of 20 placentas from women who reported heavy drinking during early pregnancy compared to those from 20 women who abstained from alcohol throughout pregnancy. The Safe Passage Study is the first prospective, longitudinal, large-scale, and hypothesis-driven study of the relationship between prenatal alcohol toxicity and mortality and morbidity in the human fetus and infant. Upon completion 12,000 pregnant women will be enrolled in PASS and placenta samples will be collected for a random subset (~2700) from high-risk populations for prenatal alcohol exposure, SIDS, stillbirth, and FASD in a prospective study with follow-up of their infants to one postnatal year. Thus this is an ideal setting for this and future studies of placenta methylation changes due to alcohol exposure and their effects on fetal health.